The invention relates to a pane, in particular a vehicle window pane, with a transparent, electrically conductive coating and low transmission attenuation for electromagnetic radiation in the high-frequency range. The invention further relates to a method for producing such a pane and its use.
Current motor vehicles require a large number of technical devices for sending and receiving electromagnetic radiation for the operation of basic services such as radio reception, preferably in the bands AM, FM, or DAB, mobile telephony in the bands GSM 900 and DCS 1800, UMTS and LTE as well as satellite-supported navigation (GPS) and WLAN.
At the same time, modern vehicle glazings increasingly have all-sided and full-surface electrically conductive coatings transparent to visible light. These transparent, electrically conductive coatings protect, for example, interiors against overheating due to sunlight or against cooling, by reflecting incident thermal radiation, as is known from EP 378917 A. Transparent, electrically conductive coatings can effect targeted warming of the pane by application of an electrical voltage, as is known from WO 2010/043598 A1.
Common to the transparent, electrically conductive coatings is the fact that they are also impermeable to electromagnetic radiation in the high-frequency range. An all-sided and full-surface glazing of a vehicle with transparent, electrically conductive coatings renders transmission and reception of electromagnetic radiation in the interior no longer possible. For the operation of sensors such as rain sensors, camera systems, or fixed antennas, one or two localized regions of the electrically conductive, transparent coating are de-coated. These de-coated regions form a so-called communication window or data transmission window and are known, for example, from EP 1 605 729 A2.
Since the transparent, electrically conductive coatings affect the coloring and reflectance of a pane, communications windows are visually very conspicuous. Disruptions in the driver's field of view, which impair driving safety and which must absolutely be avoided, can result from de-coated regions. Consequently, communication window are arranged at inconspicuous positions on the pane, for example, in the region of the inside rearview mirror of a windshield, and covered by black imprints and plastic screens.
Such communication windows are too small to enable the transmission and reception of high-frequency electromagnetic radiation, such as is necessary, for example, for mobile telephony and satellite-supported navigation. However, the user expects to be able to operate mobile telephones at any position in the interior of a vehicle.
From EP 0 717 459 A1, US 2003/0080909 A1, and DE 198 17 712 C1, panes with a metal coating are known, all of which have grid-formed de-coating of the metal coating. The grid-formed de-coating acts as a low pass filter for incident high-frequency electromagnetic radiation. The distances between the grid elements are small compared to the wavelength of the high-frequency electromagnetic radiation and thus a relatively large fraction of the coating is patterned and vision through the pane is relatively greatly impaired. The de-coating of a relatively large fraction of the layer is tedious and cost intensive.